In the 21st century, a natural disaster such as a huge flood, an earthquake, tsunamis (submarine earthquake), etc. occurs throughout the world, causing tremendous damages.
An effective prevention method or a construction method is not yet developed until now, so the damages continue to increase. We can dare say that no places in the world are stable from the natural disaster.
When tsunamis occurs owing to the earthquake at the sea and hits a part of lowland near a shore, there is not any means to prevent such tsunamis. The regions that the tsunamis hit are terribly devastated not leaving any traces of a facility or people, so such devastated regions look miserable and are hard to recover.
The above mentioned problems cannot be resolved with a so-far developed conventional technology, and since it takes a long construction period and a huge amount of construction costs is required, so a regrettable and unhappy accident does not stop in the world.
FIGS. 1 to 3 are cross sectional views illustrating a state that a conventional embankment is destroyed owing to the erosion by seawater when waves or rainwater hit. In case of an ordinary embankment, as the erosion at the lower side of the embankment repeats owing to waves or running water, the embankment is likely to be destroyed as shown in FIG. 1.